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Organic and non-organic foods are compositionally different, says new study

A new analysis appears to refuel the debate about the nutritional value
of organic versus conventional foods, by finding that organic crops and crop-based foods contain
up to 69% more of certain antioxidants, are four times less likely to contain pesticide residue,
and have significantly lower levels of the toxic heavy metal cadmium.

Led by Newcastle University in the UK, the international team of experts reports its findings
in the British Journal of Nutrition. In what is thought to be the largest study of its
kind, the researchers describe how they pooled and analyzed data from 343 studies comparing the
compositional differences of organic and conventionally grown fruit, vegetables and cereals.

"[...] choosing food produced according to organic standards can lead to increased intake of
nutritionally desirable antioxidants and reduced exposure to toxic heavy metals. This constitutes
an important addition to the information currently available to consumers which until now has
been confusing and in many cases is conflicting."

Prof. Leifert and colleagues say their findings suggest that by switching to organically grown
crop foods, and foods made from them, people would consume additional antioxidants equivalent to
eating between one and two extra portions of fruit and vegetables per day.

They would also be consuming less cadmium, one of the three metal contaminants - the other two
being lead and mercury - for which the European Commission has given maximum permitted levels in
food.

In their analysis, the team found cadmium levels were nearly 50% lower in organically grown than
conventionally grown crops.

For a crop to qualify as "organic," the grower is not allowed to protect it with synthetic
chemicals or feed it with certain mineral fertilizers (for example, nitrogen compounds, potassium
chloride and superphosphate). This is in order to reduce environmental impact from nitrates and
phosphorous, and to avoid pesticide contamination in groundwater.

Instead, organic crop growers are expected to give regular feeds of organic fertilizers, such
as manure and composts, to enrich the nitrogen in the soil by rotating legume crops, and use
non-chemical crop protection methods, such as crop rotation, mechanical weeding and biological
pest control.

Findings contradict two earlier important studies

The findings contradict those of two important studies - one published in 2009 and the other
in 2012 - that have found no substantial differences or nutritional benefits in organic over
conventionally produced foods.

The 2009 study - which was commissioned by the UK Food Standards Agency (FSA) - was the first systematic review of the
literature on organic food versus non-organic food. Researchers from the London School of
Hygiene and Tropical Medicine concluded there was currently no evidence to justify selecting
organically over conventionally produced foods on the basis of nutritional superiority.

The 2012 study was also a
literature review on organic versus conventionally produced food. There, researchers from
Stanford University School of Medicine also concluded that - apart from "weak evidence" of higher
phenol levels in organic produce - there was no significant evidence pointing to nutritional
benefits linked to the consumption of organic foods.

Prof. Leifert says research on organic versus conventionally produced food has been slow to
take off the ground and more studies have been published since these reviews:

"We benefited from a much larger and higher quality set of studies than our colleagues who
carried out earlier reviews."

For example, more than half the studies in the Newcastle-led analysis were not available to
the team that carried out the 2009 FSA-sponsored study. Prof. Leifert and colleagues also argue
that the Stanford study incorporated less than half the number of comparisons for most health-promoting nutrients.

Plus, because of the much larger quantity of data available, they were able to "use more
appropriate statistical methods to draw more definitive conclusions regarding the differences
between organic and conventional crops," says meta-analysis expert Dr. Gavin Stewart, a lecturer
in Evidence Synthesis at Newcastle.

Nutritional benefit of organic food is yet to be studied

The study did not investigate the nutritional benefits of organic food, it compared the
composition of organic food against conventionally grown food and found:

Concentrations of antioxidants such as polyphenolics were between 18-69% higher in
organically grown crops.

Concentrations of total nitrogen were 10% lower, nitrate 30% lower and nitrite 87% lower in
organic compared with conventional crops.

Pesticide residues were four times more likely to be found in conventional crops than organic
ones.

Prof. Leifert says while the findings show without doubt there are compositional differences
between organic and non-organic crops, there is now an urgent need for well-controlled human
studies that pinpoint and quantify the health impact of switching to organic food.

Critical reaction says 'the evidence is unconvincing'

Meanwhile, there has been a critical reaction from some experts about the new findings. One of
these is Dr. Alan Dangour, reader in Food and Nutrition for Global Health at the London School of
Hygiene & Tropical Medicine, and first author of the 2009 FSA paper.

Dr. Dangour says the new review mixes good quality data with bad quality data in a way that is
"highly problematic" and in his view significantly weakens the researchers' conclusions.

In an "expert reaction"
published by Science Media Centre, he also says the new study has overstated the significance of
its findings, because there is no good evidence to support the idea that consuming more
antioxidants and polyphenols has important benefits for public health, and there is no robust
evidence that having more of them in the human diet reduces the risk of cardiovascular disease,
cancer and other chronic conditions.

"All natural products vary in their composition for a wide variety of reasons," says Dr.
Dangour, adding that the paper "provides no convincing evidence to refute our earlier finding,"
which he says were fully supported by the 2012 Stanford study, that there are "no important
differences in nutrient content between organically and conventionally produced foods."

The study was funded jointly by the European Framework 6 programme and the Sheepdrove
Trust.

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